SIBO Nutritionist NYC: A Functional Nutrition Approach to Healing Small Intestinal Bacterial Overgrowth
Struggling with bloating, constipation, IBS, or recurring SIBO? Work with a NYC Functional Nutritionist specializing in root-cause digestive healing.
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Why SIBO Is More Than Just Bloating
If you have been told you have IBS, struggle with chronic bloating, constipation, diarrhea, reflux, food sensitivities, brain fog, fatigue, or feel like you are reacting to everything you eat, Small Intestinal Bacterial Overgrowth (SIBO) may be a key piece of the puzzle.
Many people spend years trying elimination diets, probiotics, digestive supplements, and medications without lasting relief, because the true drivers of SIBO are never identified.
As a Functional Nutritionist, I help clients uncover and address the underlying factors contributing to SIBO so they can improve digestive function, reduce inflammation, and create sustainable healing. SIBO is one piece of the bigger picture, you can read more about my full approach on my gut health page.
What Is SIBO?
SIBO (Small Intestinal Bacterial Overgrowth) occurs when excessive bacteria colonize the small intestine. The small intestine is designed primarily for digestion and nutrient absorption. When bacteria that normally belong in the large intestine migrate into the small intestine, they begin fermenting carbohydrates prematurely.
This fermentation produces gases including:
- Hydrogen
- Methane
- Hydrogen sulfide
These gases contribute to digestive symptoms and can impact the nervous system, immune system, hormones, thyroid function, and overall quality of life. According to the American College of Gastroenterology, SIBO is characterized by excessive bacterial growth in the small bowel associated with gastrointestinal symptoms.
Common Symptoms of SIBO
Digestive Symptoms
- Bloating that worsens through the day
- Excessive gas and burping
- Reflux
- Abdominal pain
- Constipation, diarrhea, or both
- Food sensitivities
- Nausea
Whole-Body Symptoms
- Brain fog and fatigue
- Anxiety and low mood
- Histamine intolerance
- Joint pain
- Skin conditions
- Nutrient deficiencies
- Thyroid dysfunction and autoimmune flares
If your labs keep coming back normal while these symptoms continue, deeper investigation may be warranted.
The Three Types of SIBO
Hydrogen-Dominant SIBO
Typically associated with loose stools, diarrhea, bloating, gas, and abdominal discomfort.
Methane-Dominant SIBO (Now Called IMO)
Methane is produced by archaea rather than bacteria, which is why many experts now call this Intestinal Methanogen Overgrowth (IMO). Symptoms commonly include chronic constipation, incomplete bowel movements, severe bloating, weight gain, and sluggish digestion.
Research consistently shows methane production is strongly associated with constipation severity.
Hydrogen Sulfide SIBO
Often associated with rotten-egg-smelling gas, sulfur sensitivity, diarrhea, histamine symptoms, and fatigue.
SIBO Testing: How We Confirm What Is Actually Going On
One reason SIBO is so often missed is that standard bloodwork and a routine colonoscopy do not detect it. Confirming SIBO, and identifying which type you have, usually comes down to breath testing, paired with a careful look at your history and symptoms. Knowing whether you are dealing with hydrogen, methane (IMO), or hydrogen sulfide changes the entire plan, so testing is not an afterthought. It is what makes a protocol precise instead of a guess.
Breath testing, explained simply
A SIBO breath test measures the gases bacteria and archaea produce when they ferment a sugar substrate. You drink a measured solution, then provide breath samples at timed intervals. The pattern and timing of the gases tell us whether there is overgrowth in the small intestine and which gas is dominant.
Lactulose vs glucose: Lactulose travels the full length of the small intestine, so it can pick up overgrowth further down. Glucose is absorbed higher up, so it tends to be more specific but can miss distal overgrowth. Each has trade-offs, and the right choice depends on your symptom picture.
The three gases: Hydrogen points toward classic hydrogen-dominant SIBO. Elevated methane reflects IMO, which tracks closely with constipation. Hydrogen sulfide, measured on newer tests, is linked to that distinctive sulfur quality and sometimes diarrhea.
What the numbers mean
Results are not a simple positive or negative. We look at how high the gases rise, how quickly, and how that maps to what you are actually experiencing. A test result only matters in the context of your history, which is why I read them alongside your full picture rather than treating a single number as the whole story.
In-person in NYC or at-home, nationwide
Breath testing can be done with an at-home kit shipped to you, which means clients across New York City and nationwide can complete it without a lab visit. For local clients, we can coordinate testing as part of working together in person at my Manhattan office. Either way, I help you interpret the results and turn them into a plan, rather than leaving you with a printout and no direction.
Not sure whether SIBO is even the right thing to test for yet? The free Root Cause Quick Scan can help point you toward which system to investigate first.
Why SIBO Keeps Coming Back
One of the biggest misconceptions about SIBO is that killing bacteria is enough. Research shows recurrence rates can approach 40 to 45 percent if underlying causes are not addressed.
This is where functional medicine differs from a symptom-focused approach. The real question is: why did SIBO develop in the first place?
Root Causes of SIBO
1. Impaired Migrating Motor Complex (MMC)
The MMC is the gut's housekeeping wave, sweeping bacteria and debris through the digestive tract between meals. When it is impaired, bacteria accumulate in the small intestine. Dr. Mark Pimentel's research highlights impaired motility as one of the primary mechanisms driving recurrent SIBO.
2. Chronic Stress and Nervous System Dysregulation
When the nervous system is stuck in a chronic stress response, digestive enzyme and stomach acid production decline, motility slows, and blood flow shifts away from digestion. Gut healing requires addressing nervous system health, not simply antimicrobial treatment.
3. Hypothyroidism and Hashimoto's Disease
Low thyroid hormone slows gastrointestinal transit time, and research consistently shows a strong relationship between hypothyroidism and SIBO. This is one reason many Hashimoto's patients experience bloating, constipation, reflux, and food sensitivities.
4. Food Poisoning and Post-Infectious IBS
A significant percentage of SIBO cases begin after food poisoning, traveler's diarrhea, or other GI infections. Certain bacterial toxins may damage the enteric nervous system and impair motility long after the infection resolves.
5. Low Stomach Acid
Stomach acid is one of the body's first defenses against bacterial overgrowth. Aging, chronic stress, H. pylori infection, long-term acid-suppressing medications, and nutrient deficiencies can all reduce it.
6. Bile Insufficiency
Bile does more than digest fats, it also helps regulate microbial populations in the GI tract. Poor bile flow can contribute to constipation, fat malabsorption, dysbiosis, and SIBO recurrence.
7. Previous Antibiotic Use
While antibiotics can be lifesaving, repeated courses may alter microbial diversity and increase susceptibility to dysbiosis and bacterial overgrowth.
The Functional Medicine Perspective on SIBO
Functional medicine views SIBO as a manifestation of deeper dysfunction rather than an isolated diagnosis. The goal is not simply to eradicate bacteria. The goal is to create an environment where overgrowth cannot easily return.
My Functional Nutrition Framework for SIBO
Stabilize the Foundation
Before aggressive protocols, we stabilize blood sugar (which otherwise drives cortisol dysregulation, inflammation, and cravings) and support the nervous system through stress reduction, breathwork, sleep, and vagal tone.
Optimize Digestion
Depending on the individual, support may include digestive enzymes, stomach acid support, bile support, and nutrient repletion. Many people with SIBO have compromised digestion long before overgrowth develops.
Address Overgrowth
Treatment is individualized and may involve collaboration with your providers. Approaches discussed in the literature include antibiotic therapy, herbal antimicrobials, dietary interventions, and motility support. Some herbal approaches show efficacy comparable to conventional treatment in certain patients, though more research is needed.
Repair and Rebuild
This is where many people stop too early. Long-term healing often requires restoring microbial diversity, supporting gut barrier integrity, reintroducing foods strategically, optimizing fiber, and supporting immune regulation.
How We Work Together
Comprehensive Assessment
We review your full history, prior testing, diet, medications, and the timeline of your symptoms, then decide which testing will actually move your plan forward. The goal is to understand why the overgrowth developed, not just that it is there.
Your Personalized Protocol
Based on your type of SIBO and your root causes, I build a step-by-step plan across nutrition, targeted support, motility, and the nervous-system and digestive foundations, sequenced so it is doable inside a real, busy life. No 30-supplement overwhelm, no endless restriction.
Ongoing Refinement
SIBO healing is rarely linear, and recurrence is common when people stop too early. We track your symptoms, retest when it helps, and adjust through the repair-and-rebuild phase so the relief actually holds rather than cycling back.
SIBO, Autoimmune Disease, and Chronic Inflammation
Emerging research continues to highlight connections between gut dysfunction and immune dysregulation. Individuals with SIBO commonly present with Hashimoto's thyroiditis, rheumatoid arthritis, Sjogren's syndrome, psoriasis, inflammatory bowel disease, and chronic fatigue.
If you are navigating Hashimoto's or another autoimmune condition alongside gut symptoms, you may also want to explore my autoimmune nutrition page.
A SIBO Nutritionist for New York City
I work with clients across Manhattan and throughout New York City, in person at my office at 136 Madison Avenue, and virtually for clients across the city and nationwide. The pace and pressure of NYC life is not a side note when it comes to SIBO. Chronic stress directly slows the migrating motor complex, lowers stomach acid, and shifts blood flow away from digestion, the exact mechanisms that let bacteria overgrow and keep coming back.
That is why a plan built for someone juggling a demanding career and a full life has to fit the life, not fight it. My SIBO protocols are realistic inside a real NYC schedule: practical around eating out and travel, paced so you are not white-knuckling restriction, and focused on the nervous-system and motility foundations that actually prevent recurrence.
Whether you were recently diagnosed, have relapsed after a previous round of treatment, or suspect SIBO is behind bloating and IBS that no one has gotten to the bottom of, you deserve more than another elimination diet. Let us find what is actually driving it, and build something that lasts.
Frequently Asked Questions
Can SIBO be permanently cured?
The better question is whether the underlying drivers have been addressed. When motility issues, stress, thyroid dysfunction, digestive insufficiency, and dietary triggers remain unresolved, recurrence becomes more likely.
Should I stay low-FODMAP forever?
No. Most experts view low-FODMAP as a short-term symptom-management strategy rather than a lifelong solution. Long-term restriction may reduce microbial diversity and nutritional variety.
Are probiotics helpful?
It depends on the individual. Research remains mixed, and probiotic recommendations should be personalized based on symptoms, history, and treatment stage.
How is SIBO tested, and do I need a doctor to order it?
SIBO is most commonly confirmed with a breath test measuring hydrogen and methane (and, on newer tests, hydrogen sulfide). It can be done with an at-home kit, so you do not necessarily need a separate doctor visit to get started. I help you choose the right test and interpret what the results mean for your plan.
What is the difference between SIBO and IMO?
IMO (intestinal methanogen overgrowth) is what used to be called methane-dominant SIBO. Methane is produced by archaea rather than bacteria, and it tends to drive constipation rather than diarrhea. It often responds to a different approach, which is why identifying the type before starting a protocol matters.
Can you work alongside my gastroenterologist?
Absolutely. Functional nutrition complements medical care, it does not replace it. I do not diagnose disease or change medications, that stays with your physician. What I add is the nutrition, motility, and root-cause layer a typical GI visit does not have time for, and I am glad to coordinate.
Do you see SIBO clients in person in NYC or virtually?
Both. I see clients in person at 136 Madison Avenue in Manhattan and virtually across New York City and nationwide, with breath testing available by at-home kit wherever you are.
Why Work With Dr. Sarah Khan, PhD, MBA?
I specialize in helping women and men uncover the root causes behind chronic digestive symptoms, autoimmune disease, hormone imbalances, fatigue, and inflammation. My approach combines functional nutrition, evidence-based research, root-cause investigation, gut-brain-nervous-system support, autoimmune and thyroid expertise, and personalized nutrition and lifestyle strategies.
Rather than chasing symptoms, we work together to understand why your body is struggling and create a sustainable path toward healing.
Ready to Get to the Root Cause of SIBO?
If you are tired of bloating after every meal, reacting to foods, or feeling stuck despite trying multiple approaches, let's uncover what is driving your symptoms.
Book a Free Discovery Call
“I have noticed such a difference in the symptoms I came to her for, and am blown away by her knowledge!”
I have worked with Sarah personally and also often send my clients her way as I truly believe in her and her practice. She takes amazing care of her clients and genuinely cares. She is truly amazing, I cannot recommend her enough!
Deanna D.
